This invention relates to an electrical apparatus, and more particularly, to an electrical apparatus provided with heat pipe cooling means.
It is well-known to those skilled in the art that electrical apparatus, such as distribution transformers and the like, generate considerable heat during operation. It is also well-known that it is necessary to dissipate this heat to prevent the destruction of the electrical apparatus. Normally, the heat is dissipated by air cooling. For example, by pole or pad mounting of the electrical apparatus. When such apparatus is placed below ground, normally vaults are utilized. Grills are provided over the vaults in order to circulate cooling air into vaults and about the electrical apparatus. In all such instances, the size of the container or enclosure for electrical apparatus must provide sufficient area in contact with the air to provide adequate cooling.
When the electrical apparatus is directly buried in the ground, the cooling depends solely on the conduction of the heat from the enclosure of the electrical apparatus through the surrounding soil and to the atmosphere above. In general, cooling by this means is less efficient, thus, larger tanks or enclosures have been required for buried transformers when compared to the enclosures of electrical apparatus of the same rating cooled by air. For buried transformers, since the heat must be conducted through the soil to the atmosphere, the top of the enclosure is the closest surface to the soil-atmosphere interface and thus would be the most efficient heat transfer surface. However, the air space within the transformer enclosure greatly restricts the heat transfer from this surface.
Recently, it has been suggested that buried tanks should be substantially elongated to provide greater surface area in contact with the ground or soil; where the tank is positioned in a substantially constant moisture area. See U.S. Pat. No. 3,443,157. The elongation of the tank is said to improve movement of the insulating fluid and provide better contact between the moving insulating fluid and the entire outer wall of the tank, thus, improving heat conduction. However, the elongated transformer tank depends entirely on the heat conduction between the tank wall and the ground. Thus, the cooling of such device will be dependent on the total surface area of the tank which is in contact with the ground.
It has recently been discovered that more efficient cooling of electrical apparatus can be obtained through the use of heat pipes. Using the heat pipe particularly as a portion of the enclosure of the electrical apparatus will provide greater cooling while not being as dependent on the overall surface area of the electrical apparatus enclosure.
It is therefore, a principle object of this invention to provide an electrical apparatus utilizing heat pipe cooling.
A further object of this invention is to provide an electrical apparatus where the heat pipe used for cooling is part of the apparatus enclosure.
A still further object of this invention is to provide a buried transformer where the cooling of such transformer is provided by a heat pipe formed as part of the transformer.